Unusual Properties of X-Ray Emission near the Galactic Center
Unusual Properties of X-Ray Emission near the Galactic Center
复制标题
银河系中心附近 X 射线发射的异常特性
DOI：
10.1093/pasj/52.4.l25
复制
发表时间：
2000
期刊：
影响因子：
--
通讯作者：
T. Sonobe
中科院分区：
文献类型：
--
作者：
Y. Tanaka;K. Koyama;Y. Maeda;T. Sonobe
在Koyama等人的第一份报告（1996，AAA 65.155.208）之后，详细研究了ASCA卫星观测到的银河系中心1 ^{\circ}\times1^{\circ}$区域的X射线光谱。观测到的光谱包含各种元素的类氦和类氢离子的突出发射线，并且在整个区域基本上是相同的。如果观察到的光谱是来自热等离子体的热发射，则需要多温度等离子体成分，每个成分处于不同的电离度并且具有不同的吸收量。绝热冷却和电离度的系统性变化的情况下，该地区是对银河系中心的起源热等离子体。类氦和类氢铁K线的显着增宽被证实。线宽对应的均方根速度为3300 $ km~s$^{-1}$，这远远超过了Ginga卫星测量的等离子体中的声速kT 14 $ keV。这些事实使人们对观测到的X射线发射的热起源产生了怀疑。
The X-ray spectrum in a $1^{\circ}\times1^{\circ}$ region of the Galactic center observed with the ASCA satellite is examined in detail, following the first report by Koyama et al. (1996, AAA 65.155.208). The observed spectrum contains prominent emission lines from helium-like and hydrogen-like ions of various elements, and is essentially the same all over the region. If the observed spectrum is thermal emission from hot plasmas, it requires multi-temperature plasma components, each at a different degree of ionization and with a different amount of absorption. The absence of adiabatic cooling and of systematic changes in the degree of ionization over the region is against the Galactic center origin of hot plasmas. A significant broadening of the helium-like and hydrogen-like iron K-lines is confirmed. The line width corresponds to a rms velocity of $\sim3300$ km~s$^{-1}$, which far exceeds the sound velocity in a plasma of $kT\sim14$ keV measured with the Ginga satellite. These facts cast doubt on a thermal origin of the observed X-ray emission.